1. Field of the Invention
The present invention is related to a method for forming a thin-film transistor array substrate, and more particularly, to a method for forming a thin-film transistor array substrate required only three masks.
2. Description of the Prior Art
As the manufacturing technique of flat panel displays advances, it has become effortless to offer flat panel displays characterized in large size, high resolution, and high brightness. Throughout the manufacturing process, quality control is considered to be a critical factor to improve the production yield rate in addition to product dimension and quality. Generally speaking, a thin-film transistor liquid crystal display (TFT-LCD) mainly contains three processes including: thin-film transistor array engineering, cell engineering, and module engineering. Among them, thin-film transistor array engineering is achieved by forming an array-shaped thin-film transistor circuit on a glass substrate, which includes a plurality of scanning lines, signal lines, and pixel structures defined by intersected scanning lines and signal lines.
In the conventional art, a pixel structure of the thin-film transistor circuit has to be fabricated by five masks i.e. five photolithographic-and-etching processes, and each of them is provided with different patterns. As the requirement of large-sized flat panel displays grows, masks for manufacturing of large-sized flat panel displays have to be enlarged accordingly. Moreover, the cost for large-sized masks is higher and it is necessary to use different masks in each mask fabrication step. Consequently, it is hard to lower the cost for fabricating large-sized flat panel displays subjected to the quantity and cost of the masks.